kernel/irq/autoprobe.c

   1 /*
   2  * linux/kernel/irq/autoprobe.c
   3  *
   4  * Copyright (C) 1992, 1998-2004 Linus Torvalds, Ingo Molnar
   5  *
   6  * This file contains the interrupt probing code and driver APIs.
   7  */
   8
   9 #include <linux/irq.h>
  10 #include <linux/module.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/delay.h>
  13 #include <linux/async.h>
  14
  15 #include "internals.h"
  16
  17 /*
  18  * Autodetection depends on the fact that any interrupt that
  19  * comes in on to an unassigned handler will get stuck with
  20  * "IRQ_WAITING" cleared and the interrupt disabled.
  21  */
  22 static DEFINE_MUTEX(probing_active);
  23
  24 /**
  25  *      probe_irq_on    - begin an interrupt autodetect
  26  *
  27  *      Commence probing for an interrupt. The interrupts are scanned
  28  *      and a mask of potential interrupt lines is returned.
  29  *
  30  */
  31 unsigned long probe_irq_on(void)
  32 {
  33         struct irq_desc *desc;
  34         unsigned long mask = 0;
  35         unsigned int status;
  36         int i;
  37
  38         /*
  39          * quiesce the kernel, or at least the asynchronous portion
  40          */
  41         async_synchronize_full();
  42         mutex_lock(&probing_active);
  43         /*
  44          * something may have generated an irq long ago and we want to
  45          * flush such a longstanding irq before considering it as spurious.
  46          */
  47         for_each_irq_desc_reverse(i, desc) {
  48                 spin_lock_irq(&desc->lock);
  49                 if (!desc->action && !(desc->status & IRQ_NOPROBE)) {
  50                         /*
  51                          * An old-style architecture might still have
  52                          * the handle_bad_irq handler there:
  53                          */
  54                         compat_irq_chip_set_default_handler(desc);
  55
  56                         /*
  57                          * Some chips need to know about probing in
  58                          * progress:
  59                          */
  60                         if (desc->chip->set_type)
  61                                 desc->chip->set_type(i, IRQ_TYPE_PROBE);
  62                         desc->chip->startup(i);
  63                 }
  64                 spin_unlock_irq(&desc->lock);
  65         }
  66
  67         /* Wait for longstanding interrupts to trigger. */
  68         msleep(20);
  69
  70         /*
  71          * enable any unassigned irqs
  72          * (we must startup again here because if a longstanding irq
  73          * happened in the previous stage, it may have masked itself)
  74          */
  75         for_each_irq_desc_reverse(i, desc) {
  76                 spin_lock_irq(&desc->lock);
  77                 if (!desc->action && !(desc->status & IRQ_NOPROBE)) {
  78                         desc->status |= IRQ_AUTODETECT | IRQ_WAITING;
  79                         if (desc->chip->startup(i))
  80                                 desc->status |= IRQ_PENDING;
  81                 }
  82                 spin_unlock_irq(&desc->lock);
  83         }
  84
  85         /*
  86          * Wait for spurious interrupts to trigger
  87          */
  88         msleep(100);
  89
  90         /*
  91          * Now filter out any obviously spurious interrupts
  92          */
  93         for_each_irq_desc(i, desc) {
  94                 spin_lock_irq(&desc->lock);
  95                 status = desc->status;
  96
  97                 if (status & IRQ_AUTODETECT) {
  98                         /* It triggered already - consider it spurious. */
  99                         if (!(status & IRQ_WAITING)) {
 100                                 desc->status = status & ~IRQ_AUTODETECT;
 101                                 desc->chip->shutdown(i);
 102                         } else
 103                                 if (i < 32)
 104                                         mask |= 1 << i;
 105                 }
 106                 spin_unlock_irq(&desc->lock);
 107         }
 108
 109         return mask;
 110 }
 111 EXPORT_SYMBOL(probe_irq_on);
 112
 113 /**
 114  *      probe_irq_mask - scan a bitmap of interrupt lines
 115  *      @val:   mask of interrupts to consider
 116  *
 117  *      Scan the interrupt lines and return a bitmap of active
 118  *      autodetect interrupts. The interrupt probe logic state
 119  *      is then returned to its previous value.
 120  *
 121  *      Note: we need to scan all the irq's even though we will
 122  *      only return autodetect irq numbers - just so that we reset
 123  *      them all to a known state.
 124  */
 125 unsigned int probe_irq_mask(unsigned long val)
 126 {
 127         unsigned int status, mask = 0;
 128         struct irq_desc *desc;
 129         int i;
 130
 131         for_each_irq_desc(i, desc) {
 132                 spin_lock_irq(&desc->lock);
 133                 status = desc->status;
 134
 135                 if (status & IRQ_AUTODETECT) {
 136                         if (i < 16 && !(status & IRQ_WAITING))
 137                                 mask |= 1 << i;
 138
 139                         desc->status = status & ~IRQ_AUTODETECT;
 140                         desc->chip->shutdown(i);
 141                 }
 142                 spin_unlock_irq(&desc->lock);
 143         }
 144         mutex_unlock(&probing_active);
 145
 146         return mask & val;
 147 }
 148 EXPORT_SYMBOL(probe_irq_mask);
 149
 150 /**
 151  *      probe_irq_off   - end an interrupt autodetect
 152  *      @val: mask of potential interrupts (unused)
 153  *
 154  *      Scans the unused interrupt lines and returns the line which
 155  *      appears to have triggered the interrupt. If no interrupt was
 156  *      found then zero is returned. If more than one interrupt is
 157  *      found then minus the first candidate is returned to indicate
 158  *      their is doubt.
 159  *
 160  *      The interrupt probe logic state is returned to its previous
 161  *      value.
 162  *
 163  *      BUGS: When used in a module (which arguably shouldn't happen)
 164  *      nothing prevents two IRQ probe callers from overlapping. The
 165  *      results of this are non-optimal.
 166  */
 167 int probe_irq_off(unsigned long val)
 168 {
 169         int i, irq_found = 0, nr_of_irqs = 0;
 170         struct irq_desc *desc;
 171         unsigned int status;
 172
 173         for_each_irq_desc(i, desc) {
 174                 spin_lock_irq(&desc->lock);
 175                 status = desc->status;
 176
 177                 if (status & IRQ_AUTODETECT) {
 178                         if (!(status & IRQ_WAITING)) {
 179                                 if (!nr_of_irqs)
 180                                         irq_found = i;
 181                                 nr_of_irqs++;
 182                         }
 183                         desc->status = status & ~IRQ_AUTODETECT;
 184                         desc->chip->shutdown(i);
 185                 }
 186                 spin_unlock_irq(&desc->lock);
 187         }
 188         mutex_unlock(&probing_active);
 189
 190         if (nr_of_irqs > 1)
 191                 irq_found = -irq_found;
 192
 193         return irq_found;
 194 }
 195 EXPORT_SYMBOL(probe_irq_off);
 196